wire drawing machine

Basic principalsThe art or process of wire drawing like the name implies is to draw a wire of a bigger diameter through a hole with smaller diameter hereby reducing the diameter through plastic deformation while the volume remains the same.

Wednesday, September 15, 2010

extile techniques are traditionally worked with fibers such as linen, cotton and silk. However, they can also be applied to metal.

I weave high karat gold and platinum sheet and wire by hand. The process of weaving creates "fabric". I shape that "fabric" into ribbons and ruffles, spirals and loops, which become earrings, brooches, necklaces and pendants. I create two collections of limited production and one-of-a-kind jewelry, each based on a different technique.

Weaving is the interlacing of two sets of elements, one vertical and one horizontal. In my first collection, the vertical element - the warp - is sheet that is cut into strips or wedges. The horizontal element - the weft - is multiple strands of thin wire twisted together. The pattern is a Plain Weave (Figure 1), in which the wire crosses over the sheet, then under the sheet, continuing over one warp, under one warp. The strong color contrast in my Large Ruffle Brooch (Figure 2) makes it easy to read the Plain Weave: the warp, the vertical element, is sterling silver sheet; the weft, the horizontal element, is comprised of red magnet wire (resin coated copper) twisted with black silk thread.

Figure 2 Large Ruffle Brooch Barbara M. Berk

When the warp and the weft are the same metal, as in the 18kt gold Ruffle Brooch (Figure 3) it is not as easy to read the pattern. The lighting on the brooch highlights the warp strips; the wire weft can be seen at the end of the bottom ruffle: it is composed of four strands of thin wire twisted together. This creates a thicker weft, which is more malleable than a single wire of the same diameter. As the twisted wire weft crosses under the sheet, the sheet is pressed down over it, which locks the weft in place and adds strength to the piece. (The Ruffle Brooch warp is 36 gauge sheet, the weft is 26 gauge round wire.)

My second collection is based on a technique that also uses two elements, but both elements are single strands of wire: a thin wire weft and a thicker wire for the warp. The pattern is called Soumak: it is an ancient rug weaving technique named for Shemakha, the city in Azerbaijan in which it originated. Figure 4 shows the weft traveling over two warps and back around one warp, thereby wrapping around each of the warps in turn. The Bow Brooch (Figure 5) is a Soumak weave: the pattern is easiest to see where the ends flare out, in the lacy area above the pearls. The thicker warp wire (20 gauge) is 18kt gold, providing the strength; the thinner weft wire (28 gauge) is 22kt gold, providing the malleability needed to do the tight wrapping that creates a dense weave. The warp is the skeleton, the weft is the skin; the two alloys in combination create a structurally sound piece.

Figure 4 Soumak: continuous wire weft wraps around each wire warp

With both Plain Weave and Soumak, each piece is woven individually. The weaving is done flat: the Plain Weave rests on a thick sheet of plastic, so as not to mar the metal during weaving, and the Soumak is supported in a small vice. Neither pattern is woven on a loom. Rather, both patterns rely on an open-ended warp system, which allows the weft to be easily placed over and under the warps without distorting the warps in the case of the Plain Weave, or easily wrapped around and pushed down the warps in the case of the Soumak. When the weaving is completed, the edges are finished and then the woven "fabric" is shaped into a sculptural form. While the metal is soft enough to weave and manipulate with fingers, it work hardens in the process of weaving and again in the process of shaping, resulting in a stable piece.

Figure 5 Bow Brooch Barbara M. Berk; photo credit Dana Davis

Weaving can be executed with sheet as both warp and weft; with sheet warp and wire weft (as I do in my Plain Weave); with wire warp and sheet weft; with wire as both warp and weft (as I do in my Soumak); with combinations of sheet and wire warps and/or wefts; and either on-loom or off-loom. One can create patterns in the weave by changing the interaction between warp and weft, i.e., varying the number of warps the weft "skips" and varying the rotation of the "skips". One can weave the metal flat and then shape it, or one can create a 3-dimensional form during the weaving process.

Textile techniques in general, and weaving in particular, offer the opportunity to work in new ways with familiar forms of sheet and wire. In the process of mastering these techniques, one can explore color, pattern, texture, structure and scale.

The trick to drawing wire by hand is to grasp the tapered end that sticks out the front of the drawplate with the pliers in such a way that there are some 5 mm of play; of movement back and forth to the drawplate. Push the draw tongs up to the plate so that when you start to draw there is a little movement before the wire begins to go through the plate. If it starts drawing with a jerk the inertia carries the wire on and as long as you keep on moving it will not break easily. If you don't start by using this jerk (usually obtained by bending the elbows and throwing your body back until it's weight going backwards starts the wire moving) it can be hard to start it. To find the correct hole to put the wire in next take the back end of the wire and test it in the front holes of the drawplate. When you find the hole it will not fit into then the correct hole is the next one down.

To make the taper on the end of the wire one may file a tapered groove into a flat slope on the bench pin, lay the end of the wire in it and rotate it while one files the wooden slope. This automatically generates a smooth and even taper and is how pinstems are tapered when one only has to do one or two.

An easier method of tapering which simultaneously hardens the point somewhat and prevents its breaking off easily during drawing is to step roll the point in the wire rolls of a hand rolling mill. Roll the end in slightly, back it out and put it in again at 90o to the first direction, then go to the next smallest hole and do the same thing only not as far in on the wire. Continue in this way until you have a smooth tapered point. Tubing too can be step rolled to get a taper on the end for drawing it. One can solder the tapered end for more strength.

People use either beeswax or oil as lubricants. I prefer oil.

If you need only a few holes of an odd shaped drawplate one can be made from an old file, annealed, drilled and burred and filed to shape. The holes must taper to the back and be as polished as possible. A flex shaft is useful for this work. One can however buy drawplates from companies such as TSI (see list) for 10.00 and less which with a little work with a toothpick in the flex shaft and some steel polishing compound can be made acceptable. Eventually one is better off buying a well made one. For larger sizes of tube a hard wood, nylon or Delrin® drawplate can be made for drawing down just a few holes.

One can obtain various shapes by using a square and round drawplate. The wires start out as either round or square and are drawn together with frequent annealings until the proper shapes are achieved. For example a square or round wire is flattened, folded over, soldered to close the 'loop' and drawn through a square hole in the drawplate to produce two triangular wires. One has to work with care to make this technique work well. One can make half round wire by rolling a round wire into a thick sheet of copper on the mill, the round wire then becomes a half round wire albeit with a slight texture to the surface.

The back of a drawplate also serves as a tool for shaping tubing to tapers, both square and round if one makes an appropriate mandrel for the hole. Note that the tool is not hammered in but pushed. Your drawplate is worth more than a bezel forming tool so don't hammer into it. One can also "step draw" both wire and tubing by drawing to a certain point, pulling it back out the way it came in from and then going to the next smallest hole and repeating the process. Richard Mawdsley uses this technique to very good effect in producing stepped tubing for his complex constructed pieces.

A simple wooden device may be constructed for holding draw-plates on the end of a workbench or it can be as simple as two steel rods inserted in the bench to pull against. This frees the vise for other uses.

In many cultures one sits on the ground, draws the knees up, places the drawplate against your feet and then straightens ones legs to draw the wire. Leg muscles are much stronger than arm muscles and it is quite effective.

A draw bench is extremely useful and one may be constructed from wood and canvas or with a boat winch and board. If using steel cable instead of canvas or leather belting steps should be taken to secure the end of the cable from flying up loose and injuring someone if it is accidentally released. An Asian Indian version uses leverage and a ratcheting motion to draw wire on a carved plank on the ground.